Method of heat transfer at high temperatures



June 23, 1931. c. FIELD 1,810,912

METHOD OF HEAT TRANSFER AT HIGH TEMPERATURES Original Filed April 17.1922 3 Sheets-Sheet l iii-3;; 15

j o z E I 7? I Z' J INVENTOR [iwyfield 71m ATTORNEY C. FIELD June 23,1931.

METHOD OF HEAT TRANSFER AT HIGH TEMPERATURES Original Filed April 17.1922 3 Sheets-Sheet 2 L/ZQ 5'.

INVENTOR 1 d ATTORNEY June 23, 1931. 'c. FIELD 1,810,912

METHOD OF HEAT TRANSFER AT HIGH TEMPERATURES Original Filed April 17.1922 3 Sheets-Sheet 3 Patented June 23, 1931 UNITED STATES PATENT OFFICECROSBY FIELD, OF BROOKLYN, NEW YORK, ASSIGNOB' TO CHEMICAL MACHIIil'EBYCOB- POB-ATION, A CORPORATION OF NEW YORK I METHOD OF HEAT TRANSFER ATHIGH TELEPEBATUBES Original application filed April 17, 1922,

, 1927. Serial My present invention is more or less closely related tocertain heat transferring operations of the clases described in myPatent No. 1,403,471, granted J anuar 10, 1922. In the present case, asinmy Pat nt No: 1,619,- 661 granted March 1, 1927, on application Ser.No. 553,640 filed A ril 17, 1922, of which this is a division, t e heattransferring medium is a liquid of boiling point much above that ofwater, preferably mercury; the temperatures at which heat is to betransferred are usually far above said boiling point of water; thetemperatures of heat transfer either to the transferring medium or fromthe transferrin medium, or both, are determined by the internalpressures at the boiling or the condensing points, or both; and thesepressures may be controlled either b hand manipulation 'or automaticaction 0 valves, pumps or other suitable pressure controlling devices.

My present invention includes regulating the temperature in the heattransferring-system by controlling the internal pressure by and inaccordance with the temperature of a region or substance to be heated orcooled; or by the difierence between the internal and externalpressures; and the external pressure may be atmosphere or may be onemaintained in an auxiliary part of the system by a vacuumizing or otherpressure controllin pump.

In tlie preferred embodiment and in normal operation the ressure isapproximately uniform throug out the circuit ofthe heat transfer medium,although the pressure at the boiling or heat absorption point may behigher than at the condensing or heat yielding point.

While the system may be employed partly or exclusively for cooling, therimary purpose illustrated is heating substances, for distillation,sublimation or chemical reaction which require limiting the temperaturesfor a predetermined maximum or minimum, or between a maximum and aminimum; or for different temperatures successively.

My present invention includes systems wherein there is a supplementalcondenser located beyond the primary condensing re-..

said circulating system.

Serial No. 553,640. Divided and this application filed February a,

gion and adapted to return its condensate to the circulating system. Incertain cases the supplemental condenser is beyond the ressurecontrolling valverin others it is etween the primary condensation orheat yielding} region and the pressure controllingcirculatin system andin others the return is contro ed by a valve opened only when conditionsof operation permit.

Preferably all of the systems have pumps, adapted to withdraw foreigngases and impurities from the circulation and these-are preferablyarranged to dischar e the impurities into the atmosphere wit outinterferin with return of condensate to the circulation and withoutinterferin with the desired vacuum or pressure con ltio'ns within Incertain cases the desired operation is continuously endothermic or heatabsorbing. In such case the heatin is b the condensation portion of theeye e an the control of however, concerns a'system which will auto- 35matically control the temperature of a desired region when'the operationin said region requires heating at one time and cooling at another timeunder conditions where the operation of the fluid medium must shift froma rimary condition of condensing to impart eat, .over to avsecondarycondition of boiling to absorb heat; and to do this automatically. Thisvery difiicult special case is frequently met with in the chemical 915industry. Certain chemicals in the mixture must be heated to apredetermined critical temperature. In certain cases, notably oxidationor partial oxidation of organic compounds, heating to a certain criticaltemper- 1 0 ature will initiate an exothermic or heat evolving reaction.The heat thus evolved necessarily raises the 5 temperature further andthe higher temperature thus produced may cause a decomposition of theproduct or even an explosion and in most cases it will create acondition unsuitable for the best performance of the desired reaction.Hence one part of my invention concerns'maintaining a body of liquidmedium in heat absorbing relation to the same region which is initiallyheated by condensation of the heated vapor. Where the heat transferringwall is thin sheet steel and the temperature drop between exterior andinterior is small," the two operations will come into effectsuccessively and automatically upon change of a few degrees in thetemperature of a chemical mixture, even without chan e of the internalpressures. Moreover, w ere there is automatic, thermostatic control ofpressures by and in accordance with the heat of the chemicals, as abovementioned, the regulation may be even closer.

Another feature of my invention concerns various methods .ofelectrically heating and boiling the mercury to be circulated to theregion of condensation for imparting heat therein.

The above and other features of my invention-will be more evident fromthe following description in connection with the accompanying drawings,in which 7 Figs. 1, 3, 4 and 7 are diagrammatic vie s of systemsembodying various features of my invention.

Fig. 2 is a sectional-detail on the line 2-2, Fig. 1.

F ig; 5 shows in longitudinal and cross section modifications of theiron filler pieces shown in Figs. 4 and 6.

Fig. 6 is a vertical section on the line 66, Fig. 4.

Figs. 8 and 9 are respectively end and side elevations of one form ofelectrically heated boiler. v, g

Fig. 10 is an end elevation of another form of electrically heatedboiler.

In these drawin the boiler, ipes, valves, condensers, and a other partslikely to contact with mercury are preferably of iron or steel, sincesuch materials are ordinarily not attacked or even wettedby mercury. The

various containers and pipes for performance of the heating function areunderstood to be properly heat insulated.

Fig. 1 shows a system articularly adapted for certain cases of eatingoperations where the operation is one of impartin heat and the substanceor region to be heate does nbt generate heat in excess of its ownradiation losses. That is to say, the sistem is one for continuous orintermittent eat application.

The system comprises a heat absorbing charges through pigs 12 as 9.

come in contact with it. As shown it is hermetically closed by a top 6communicating through a pipe 7 with a cooling chamber 8, the whole beingvacuumized throu h pipe 9 by a ump diagrammatically in cated at 10.istillate or sublimate caught in chamber 8 may be removed throughasuitable outlet, as for instance, the 'valve controlled pipediagrammatically indicated at 11. These parts ma be the ordina vacuumdistilling or sub imating unit, su l i as commonly em loyed in themanufacture of petroleum an coal tar products; and the usual mechanicalstirring means (not shown) may be emplo ed if desired.

While the mercury oiling element 1 may be usefully em loyed as a coolingelement for any desire heat evolving system, it is shown in this case asbeing electrically heated from any desired source of ower.

As will be evidentfrom the d i'awin the coil 3 is a down-flow condenserand 1t disfrom which the condensed mercury return flow path throughpipes 13, "14 and branch pipes 15 15, to the ends of boiler 1. Anyuncondense vapor can its further the pressure control instrumentalities.

The internal pressure is controlled b controlling the escape of such"vapor. 1X1 the present case there are two controls either of which maybe em loyed separately butwhich are especially a vantageous when einploed in combination.

'lhie vapor from 12 is discharged into i 22, from which in normaloperation of t device it will be permitted to flow through certaincontrolling devices into pi e 23, upflow condenser coil 24, vacuumingthrough pipe 25, check valve 26, pump 10 and dis charge outlet 29. Thejacket of condenser 24 is supplied with cooling water thro 11 pipe 240,which water esca es through t e pipe 246. A trap 29a may interposed inpipe 29 containing material adapted to comme with the last traces ofmercury vapor,

.thus preventing any mercury from escaping to the outer air.

The suction pump 10 is utilized to maintain in the condenser 24 and pipe23 a ressure which is usually less than atmosp eric and which in anyevent is preferably less pass up through. pipe 22 whence progress willbe determined by than the. ressureipe.22, which latter is refera I thatof t e circulating system. ne of e controls for the pressure is valve16, operated b fluid pressure through pipe 17, controlled y thethermometric or eat sensitive element 18, the. o eration of which iscontrolled by ad'usta le mechanism diagrammaticall indicated at 19.

Another control is y means of pressure relief valve 30 arranged in aparallel pipe connection 31. There is also a down-flow check valve 34 ina third parallel pipe 35 through which condensed mercury may flow backinto the system.

As shown in the drawin the pressure relief valve 30 may be set orabove-atmosphere ressures in the system as by having the weight 300 tothe light of fulcrum 301) as shown in Fi 1; or for below-atmospherepressures as w an the weight is to the left of said fulcrum. When thepredetermined pressure is exceeded the valve automatically opensandvents the vapor into pipe '23 and condenser 24. For below-atmospherepressures the pump will be operated in the usual way. Forabove-atmosphere pressures escape may be throu h pipe 27, check'valve 28and outlet 29. i check valve ma be rovided at 26 to revent accidentalback ow of gaseous ro ucts from the still into the mercury con enser 24.I

As before mentioned, valves 16 and'30 are ada ted for operation asfollows: I

ntainer 5 bein supplied with the .de-

sired amount of su stance 4 to be heated,

pump 10 is started vacuumizing the heating system throu h pipe 25,condenser 24, pipe 23, and one o the valves 1 6 or 30, which may be heldopen for'the purpose. The resistance 40 being pro is closed, current owsthrough mercury in the container 1 and also through the walls of thecontainer heating and eventually boiling the same. The hot vapor flowsthrough pipe 2 and condenser coil 3. Material 4 be-' mg cold,practically all of the mercury will be condensed; also the heatsensitive element 18 will be cold so the valve 16 will be closed.

Valve 16 will remain closed until the substance 4 is heated u to thedesired critical temperature for which the device 18 is adjusted andressure relief valve 30 will sta closed unti the internal pressure exceethat for. which said valve is set. Normally the boiling, condensing :andheating ma proceed until the internal pressure excee s that for whichvalve 30 is set and thereafter venting through 30 will control until themixture 4 ,reaches the critical temperature for which the thermostat 18is set.

Preferably the thermostat 18 will be set to control at lower pressuresthan the pressure relief valve 30. Hence when theinaterial 4 is onceheated enou h to bring the valve. 16 into action, it wil controlexclurly a usted, switch 41 against back flow sively unless or until vaor is generated excess of the capacity 0 said valve 16, in

which case the pressure relief valve will act a as an ordina safetyvalve blowing off at the predetermined higher pressure for which it isset.

Preferably the valve 16 is used for close regulation of below-atmospherepressures, pipe 23Vbeing vacuumized so that the pressures therein willalways be less than that in the circulating system. Usually valve 30will be set for control where internal pressures above atmosphere aredesired and in such dcase valve 16 may be permanently close The liquidcondensate can return through said valve 16 whenever it is open, butwhen- -54 inlpipe 2 or in pipe 31.

The container in which mercury is boiled to absorb heat is long ascompared with its ,cross section and is'formed with a central vaporcollecting dome 40 and also with reduced ends 44, 44. 'The heatingcurrent is supplied through electrodes 42, 42, mounted in insulatedblocks 43, '43, in said reduced ends 44. The reduced ends afi'ord thesmall-. est cross section and greatest heat development tends tolocalize therein; also the" return of condensate through branch pipes15,

15, is to these regions of greater heat development. The mass'of mercuryin boiler'l 'afiords a 'ath for electric current which is of so muclower resistance than any other path that the leakage losses in otherdirections are minimized but insulation ma be employed for parts abovethe level 0 the liquid mercury, as diagrammatically indicated at 50.

In the apparatus of Figs. 1 and 2, the level of the mercur is referablyat or near that indicated by otte line 46, 46. This level is high up inthe boiler, is well above the level of return pipe 13, 14, and is wellbelow the level of return pipe 12. Thus the flow of vapor and condensatethrough pipe 12 is free and unthrottled by any static back pressure ofmercury, while the body of mercury in pipes 13, 14, maintainsa liquidseal of mercury vapor through said pipes.

The system shown in Fi 3 resembles that of, Fig. 1 in many respects athas im ortant differences. Analogous elements inc ude reids gion 101 inwhich the fluid medium absorbs heat and boils, the pipe 102 for up-flowof the vapor, the gauge 139 indicatin internal pressure por condensesfor imparting heat to the material 104, the container 105 for thelatter, the ipe 112 for outlet of condensate and uncon ensed vapor, thedown flow'pi e 113 and the return pipe 114 for return ow of thecondensate to the boiler element 101, all being substantially as abovedescribed.

A In the present case the boiler 101 is heated by a current from thesecondary of transformer T, the primary of the transformer supplied withalternating current through suitable controlling devices including theswitch 141. The transformer is particularly useful because ofconvenience in ste ping down the voltage to-get correspondingy greatamperage -or heating eifect. on the mic! 101. t

The pipe 112 leads to and the pipe 113 drains out .of the bottom of atubular u flow condenser 124, which in this case is between the primaryor heating condenser 103, and the. pressure regulating devices. Theupper part of the condenser has an outlet through pipe 125 which may bevacuumized b pump 110. In place of the thermostatically controlled valve16 of Fi 1, there is a pressure relief valve 130 adjustable for ventinat the desired internal pressures, indicate by position of wei ht 1300as bein less than atmosphere. is valve may ,set for internal ressuresgreater than atmosphere by shi ting the weight to the other side of thefulcrum. When internal pressures above atmosphere are required, the pumpmay be cut oil by valves 110a, 1106. Then the outlet will be throughparallel pipe 127 which provides a by-pass from the intake 125 to thedischar 129 oflpum 110. This by-pass 127 may contro ed a ressure relief.valve 1306 adapted to be set or venting internal premures aboveatmosphere. These valves 130 and 1306 are adapted for simultaneous orsuccessive operation somewhat as valves 16 and 30 of Fig. 1, except thatthe primary valve is controlled by internal pressure instead ofthermostatically.

The uncondensed gases passing either through pump 110 or the by-pass 127flow to the residual condenser 124a. The lower end of this condenserconnects through a barometric U-leg 113a, and pipe 1136 with the returnpi 114 which leads back to the boiler 101. e level of the mercury isindicated by the dotted line 47, 47, as being near the top of boiler101; below the draina e pipe 112 and condensers 124,124w but above thebarometric U pipe 113a, and the return flow pipes 1136 and 114.

There is a pipe 129! affording an atmospheric outlet from pipe 113w,below the re-.

the worm coil 103 wherein the va-' sidual condenser 12401, but above thelevel of the mercury. Outlet pipe 129a: may have interposed therein atrap 29h; like the trap 29a in Fi 1. I

It will ie understood that the closed circuit through the residualcondenser 124a and the barometric U, 113a, may be used in conjunctionwith the system shown in Fig. 1, as may also the pipe 129a through whlchuncondensed gases may be discharged to the atmosphere.

In the system shown in Fig. 4, the vacuumizingpump 210, the supplementalcondenser 224, residual condenser 22401, the primary pressure reliefvalve 230, secondary relief valve 230a, container 205 for the material204 which is to be heated, as also the ad-- justments to be, made andthe operations to be performed, may be substant1ally the same 'as inFig. 3. It is noted, however,

that the supplemental condenser 224 is a down-flow condenser andresidual condenser 2240 is a tubular condenser instead of a worm.

The important differences are that the primary or heat impartingcondenser 203 is in an external jacket 2030; instead of the internalworm 103 and that instead of a single outlet 112 for both condensate anduncondensed vapor, there are two separate outlets, one a pipe 212' froma low point of the jacket for return of the condensate and the other apipe 212a from a high point in the jacket for escape of the uncondensedvapor.

This arrangement whereby the ressure of the liquid mercury in the jacketoes not interfere with the circulation of the condensing vapor-facilitates employment of an important feature not found in Fig. 3;namely, an arrangement whereby the normal level of the mercury,indicated byline 47-47, is substantially above the bottom of thecontainer 205, so that the lower portion of said container iscontinuously bathed in a body of liquid mercury. In normal operation,this mercury will be hot ,condensate which ma be at or near thetemperature of condensation as determined by the particular internalpressure then being maintained by the pressure regulating valves. Thisbody of condensate in the jacket is in an im ortant strategic positionin several partic ars.

- the same manner The vapor resulting from the boilin has a higherpressure vapor may circulate from the header.

the bottom p movably secured by pins 201:}; so that each the; header andmercury therein por sup 1y tube 502, the

' base of a three? important a vantage of this arrange;

. I5 ment is that the; boiler requires no insulation.

ressure controlling devices. The boiled 05 'quid is replenished throughpipe 212 after as the primary boiler 201.

free path of escape through the regu ar' vapor outlet 2120. to condenser224 and its ressure, condensation and return flow to the acket orsecondary boiler may be automatically controlled by theinstrumentalities above described for the primary boiler. Obviouslyhowever, the ad uStment of the pressure ief valves may be changed if itis desired-to conduct the heat generating reaction at a differenttemperature from that which initiated it,

' Moreover, where said reaction may be desirably contlnued at a highertemperature requiring a higher internal 'pressure of the mer vapor thesudden and great increase in the total volume of va r due to ilingjntheIiacket becoming a mercury stea of a mercury condensing device may betaken advantage of to cause control to shift to a pressure relief andtem erature than the one which controls the iiutfal heating. In suchcase the sudden increase in volume of exceed the condensing capacity ofthe first condenser, in which case a valve like 230 set for abelow-temperature pres-' sure maybe forced open continuously. and if thepumping capacity of pump 210 is also exceeded valve 230a will become thepressure determining instrumentality.

If the pressure control system of Fig. 1 be em loyed under conditionsabove describe he thermostatic valve 16 is likely to be too small tosufliciently relieve the increaslngpressure even when wide open, in

which case a back pressure'will be built up e until the pressure reliefvalve 30 becomes the controlling instrumentality In such case saidv'alve30 be set for the desired exothermic reaction temperature and willcome into operation automatically whenever said reaction commences.

Another novel feature in Fig.4 is the ri-v mary heat absorbing elementor b01812 -This is preferablyof iron and comprises a header 201 having aplurality of depending tubes 201a forming mercury containing pocketsinto and out of which mercury may These tubes are airs which areconnected across y conducting element 2016 rearranged in pair of tubeswith 201a is the rimary As indicated in Fig. 6,1; are are preferablythree such pairs of tubes, each energized by a difierent current.

valve set for a .ment is for three-phase as in Fig. 6.

that if the mercur formsa single turn secondary of a; transformer ofwhich-201d ,isthe core and usual control devices represented by switch241. Such control devices may be operated to reduce current or open thecircuit in response to excessive or sudden increases of pressure or heateither in the mercury systemor in the container 205. Such automaticregulation is also contemplated for the other s stemsdescribed herein.

Within the depending tubes are referably arran ed iron filler pieces201;: which normally fioat in the mercury. Their cross sections areshaped so as to aliord separate paths foru ward fiow of hot mercury andvapor and own-flow of cool mercury. Various cross sections suitable forthis purpose are shown in Fi 5.

Another nove arrangement for heating mercur' therein is shown in Figs. 8and 9. Here t e rimary coils 301a encircle the tubes and t e iron fillerpieces 201 together with the iron of the tubes, header and cross barconstitute the iron core of the transformer. In this case the heating isentirely by the eddy currents generated in the iron core by thereversals of magnetism thereof in response to the alternating current insaid coils 3016. In Figs. 8 and 9 the arran ea 1 10 shows a variationofthe above whereiil the primary coil 401d encircles the iron connectingbar 201?) instead of the tubes.

In the system of Fig. 4, it will be noted level were lowered below thebottom of 1acket 203 there would be no body of liquid mercury in thejacket and the entire space would be available for mercury vaporheating. Asystem better adapt d or operation with the mercury above'orbelow the bottom of the container or at any desired level is illustratedin Fig. 7.

In this figure, the boiler-501 is upright and extends from below thelowest level of mercu indicated by line 147 I47, to a point well a vsthe higher level indicated by 47, 47 the former. line bein below thebottom of the jacket 503 and t erlatter above the bottom of container505. Thisboiler 501 i forms art of a single turn secondary, circuit 0which isIcompleted through copper bar 501w which is 'of low enoughresistance to practically short circuit the rest of. the system. Thissingle secondary is ener ize by primary coil 501e, and controlled; by

cury in the system. In this system, the pressure controlling valve 530is located in the pipe 5120 between the jacket 503 and the condenser 524and, as diagrammatically indicated, it is adapted to be set forpressures either above or below atmosphere. The exhaust pump is beyondthe condenser and consists of a well-known form of barometric jetcondenser com rising the upwardly extending suction tu e 525 for thevapor, dischargin downwardly through the jet 510a in cham r 510 suppliedwith water through 0 nin 5106 controlled b valve 5100. i h is Slumberconnects wit downwardly extending tube 529 which is long enough toafford a barometric column when water is the fluid. The ipe 529 has anoutlet at 550 below the leve of the liquid in container 551. Thiscontainer has two water outlets, one 552 at the proper level to drainoff water when the mercury level is at 47, 47, and the other 553, whenit is at level 47,, 47. The mercury vapor is condensed by the water andsettles out in the container 551.

It might be returned to the system through a barometric U-tube like thatin Fig. 3, but as shown there is a hand operated valve at 554 which isopened only when the internal pressures are suitable for in-flow ofmercury without disturbing the adjustment of the ap aratus.

the ystem of Figs. 4 and 7, where a body of liquid mercury may be andpreferably is maintained in contact with the lower portion of the samecontainer which is being eated by condensation of the mercury vapor,there is special advantage in employing a vertical] arranged propellerto afford vertical (Sire ation of the mixture, andin Fig. 7 I have shownfor this purpose a screw ro- Her on the lower end of vertical s aft 1ournalled in the cover 507 and power driven through an suitable means,as for instance, a gear 72 riven by gear 73 on horizontal shaft 74 whichis supfported in a bearing 75 and may be rotated rom any desired sourceof power diagrammatically indicated by belt pulle s 76, 77, one of whichma be an idler whi e the other is keyed to sai shaft 74. The verticalcirculation thus;

rovided is important not only for mixin ut also for driving hot mixtureinto coo ing relation with. the liquid mercury for boiling the latterduring exothermic reactionsand also for displacing the cooler materialupward in heating relation with the condensing area of the containerwhen the operation is endothermic.

It willbe understood that the presence of liquid mercury in bathingcontact with the same container which is heated by condensation of hotvapor supplied from an outside source is of great importance, not onlyfor controlling the temperature during desired exothermic eactions, butalso as an ever 55 present refrigerating medium which will at 430Fahrenheit under a automatically come into operation as a safetyappliance in cases where undesired exothermic reactions may occur byaccident as in case of certain im urities in certain mixtures or in caseof faulty regulation by the pressure controlling devices.

A not uncommon case is where there is a small amount of impurity capableof oxidizing or other exothermic reaction within the range of thedesired operating temperature. 75 In such case the cooling action of theboiling mercury will be su cient to keep down the temperature until theexothermic reaction has been completed, after which the process willproceed as before. In other cases, as'where the amount of material forthe exothermic reaction is considerable, it ma be necessary to haveexpert attendance an regulation to completely take care'of thesituation. Even in cases where the dan er never materializes, theadvantage of the l lquid mercury as a precautionary safety device isobvious.

It will be understood as to all of the systems shown herein thatadjustment of heat- 9o ing current may be such as to boil mercury atrates suflicient to supply more vapor than will be condensed in theheating coil or i'acket. Such excess represents waste but unessmaintained the system controls will operate only as upper limitregulators. If, however, the vapor is always 1n excess, the workingtemperature will be kept up to the predetermined limit as well asprevented rom falling below it.

While the various systems disclosed herein are capable of being operatedeither above or below atmosphere, as heretofore explained, there aregreat advantages in emloyin them for t e operations e per ormed at orbelow atmospheric pressure, that is, for temperatures at orv below 357centigrade, the atmospheric boiling point of mercury. Hence, as-will beevident, a great variety of heating operations, particularl for chemicalreactions can be accomplis ed with the secondary yalve, as for instance,valve 30, Fig. 1, set to open at or below atmosphere. In thebelow-atmosphere operation there can be no leaks of mercury to theexterior. Any leaks must be inward into the system and an im uritiesthus introduced, are drawn o wit the excess um I condensed vapor and aregradually worked out of the system by continued olperation of thevacuumizing pump. While t e leaks are thus in the direction of safety asregards human life and are taken care of as above described, it isto beunderstood that they are highly undesirable and the greatest pos- 1 25sible care is taken to prevent them.

Inm prior Patent No. 1,619 661 I have stated that mercury vapor may beobtained pressure of only nine-tenths pounds to the square inch.

which can 195,

Higher degrees of heat may be obtained with corresponding increase inpressure. And I have also described how these pressures, required fordesired temperatures, can be maintained by a vacuum pump operated andcontrolled in the usual manner in connection with an ordinary pressuregauge which indicates the boiler pressure. While the methods claimed in.said application can be practised by manual control of the pump inconnection with the gauge, there are 1mportant advantages in employingautomatic means for the purpose. Hence my present application concernscertain varieties of automatic means which may be used for controllinginternal pressures. Also said automatic means include devices that arecapable of operation at pressures above as well as below atmosphere.Specifically considered, the principal regulating means are in thenature of relief valves and, to take care of the specific case where theinternal pressures are below-atmosphere, there are the various forms ofvacuumizing pumps. Such pumps require no special description orillustration, being well-known in the art, and they may be continuouslyoperated for predetermined low vacuum without special regulation. Itwill be noted, however, that in ordinary operation they are not requiredto maintain vacuum any greater than is necessar to give internalpressures free vent when t e relief valve is open. Hence said vacuumpumps may be supplied with automatic control mechanism to maintain onlythe required degree of vacuum; and when the valves are set forabove-atmosphere pressures, the pumps may be cut oil either by handvalves as indicated in Figs. 3 and 4, or by any desired automaticmechanism.

It will be understood that the pressure relief valves, such as 30, 130,130a, 230, 2300i,

and 530, are diagrammatically indicated as having the internal pressureon the valve element directly opposed by external atmospheric pressurewhich latter is adjustably counterbalanced or an ented by the weightedlever. It will e understood, of course, however, that various othervalveoperating means may be utilized with a view to more accurateregulation.

In systems of the type herein described, transfer of a given amount ofheat requires boiling and condensing of relatively large amounts ofmercury. Hence the velocity of the vapor flow is great and the resultingfriction may give rise to a certain amount of back pressure. Hence itwill be understood as to all of the systems the mercury level in theboiler may be somewhat below that in the pipes leadin from theCondensers and it will sometimes fie necessary to make allowance forthis.

In this same connection it may be noted that the level of the condensedmercury may be raised to a desired higher level than the mercury in theboiler b throttling of the return flow of the con ensed vapor. Forinstance, in Fig. 7 the mercury may be raised to or above the level47'47 in the condensing jacket while the mercury in the boiler is at amuch lower level by suitably adjusting a valve like 230 which can beinserted in i e 512. The back pressure could be varied by partiallyclosing a similar valve, which can be arranged in pipe 502. Preferably,however, the should be kept as small as possible so that the pressurethroughout the entire system may be more nearly uniform.

I claim:

1. The method of transferring heat which consists in imparting heat tomercury to boil ofi' mercury vapor in one region of a circulatingsystem, mercury vapor at another region of the system to condense it;and governing the temperature in the region to which the heat istransferred by governing the pressure of the condensing vapor by and inaccordance with the temperature of the latter region.

2. The method of transferring heat which consists in imparting heat tomercury to boil oil mercury vapor in one region of a circulating system,absorbing heat from the mercury vapor at another region of the system tocondense it; and governing the temperature of condensation by boilingofi amounts of mercury vapor in excess of the condensing capacity of theregion of condensation and maintaining a desired pressure in thecirculating system by venting the necessary amounts of said vapor.

3. The method specified by claim 2, and wherein the desired internalpressure is below atmosphere and a partial vacuum is maintained in theregion to which the pressure is vented.

4. The method specified by claim 2, regulating the boiling of themercury to produce a desired minimum excess of heat transferring vapor,by applying electric current of low voltage and large amperage togenerate heat in the mercury, and controlling the current to vary theamount of heat produced thereby.

5. A method of accurately controlling transformation of form or natureof chemical compounds which includes imparting heat to mercury to boiloff mercury vapor in one region of a circulating system, absorbing heatin said compound from said mercury vapor in another region of the systemto condense mercury; maintaining a body of the condensate in heatabsorbing relation to saidcompound in said latter region; and governingthe temperature in said latter region by boiling ofl' mercury in excessof the condensation while governing the interback pressure nal pressureof the condensing vapor; the

of the mercury to ensure a desired minimum excess of vapor, by applyingelectric current of low voltage andlarge amperage in heating relation tothe mercury, and

5 regulating the amount of the current so ap lied.

igned at New York city in the county of New York and State of New York,this 2nd day of February, A. D. 1927.

CROSBY FIELD.

5 regulatin boiling of the mercury to ensure a desired minimum excess ofvapor, by applying electric current of low voltage and large amperage inheating relation to the mercury, and

g the amount of the current so ap lied.

igned at New York city in the county of New York and State of New York,this 2nd day of February, A. D. 1927.

CROSBY FIELD.

CERTIFICATE OF CORRECTION.

Patent No. 1,810,912. Granted 111111523, 1931, m

CROSBY FIELD.

It is hereby certified that error appears in the printed specificationoi the above numbered patent requiring correction as follows: Pages 7and 8, strlke out lines 117 to 130, and lines 1 to 6, respectivelycompris ng clami 5; and that the said Letters Patent should be read withthis correction therein that the same may conform to the record of thecase in the Patent 0ff1ce.

Signed and sealed this 6th day of October, A. I). 1931.

M. J. Moore, (Seal) Acting Coimnissiouer of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,810,912. Granted June 23, 1931, to

CROSBY FIELD.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Pages 7and 8, strike out lines 117 to 130, and lines I to 6, respectively,comprising claim 5; and that the said Letters Patent should be read withthis correction therein that the same may conform to the record of thecase in the Patent Office.

Signed and sealed this 6th day of October, A. D. 1931.

M. J. Moore, (Seal) Acting Commissioner of Patents.

